Boats comprising means for introducing air to submerged portions of the boat bottom



ERGED July 18, 1967 E. J. VON HEIIDENS'QI'AM BOATS COMPRISING MEANS FORINTRODUCING AIR TO SUBM PORTIONS OF THE BOAT BOTTOM 5 Sheets-Sheet 1Filed June 23, 1965 Fig.3a

y 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THEBOAT BOTTOM Filed June 25, 1965 5 Sheets-Sheet 2 Flg 8 Fig 9 l 71 10 7275 73 73 y 13, 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THEBOAT BOTTOM Filed June 23, 1965 5 Sheets-Sheet 5 y 1967 I E. J. VONHEIDENSTAM 3, 3

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THEBOAT BOTTOM Filed June 23, 1965 5 Sheets-Sheet 4 --."""IIIIIZ 2 8 July18, 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TC SUBMERGED PORTIONS OF THEBOAT BOTTOM Filed June 25, 1965 s Sheets-Sheet s United States Patent 2Claims. (Cl. 114-67) Several types of partly air-borne boats are knownin the art in which the boa-t when moving over a water surface is to anessential part supported by a cushion of compressed air or other gasenclosed between portions of the boat bottom and the water.

The invention consists primarily of the provision of means to make airor other gas used for reducing friction between the boat and the waterflow along the boat botmm in such a manner that essential portions ofthe bottom are entirely carried by the intermediary of an air cushion.

One object of my invention is by said means to increase the speed ofhigh speed boats or, respectively, to diminish the motor force requiredfor a certain speed.

A further object of the invention is to provide means greatly improvingthe properties and behavior of a high speed boat which is in partcarried by air supplied to the space underneath portions of the boatbottom when the boat moves at high speed on wavy sea, and to distributeair introduced underneath the boat bottom so as to obtain favorablesupport and friction diminishing characteristics of the air.

With these and other objects in view my invention is directed to a highspeed boat of the type comprising bottom surfaces, the portions of whichin contact with water have at least in part a V-shape or a shape similarthereto, such portions of the bottom thus enclosing an angle with thecenter longitudinal vertical plane of the boat which is less than 90.More specifically, a boat according to the invention relates to the typeof high speed boat comprising a forward bottom portion which, adjacentsaid center longitudinal vertical plane, terminates in a step separatingthe forward bottom portion from a rearward bottom portion, the latteradjacent the step, being located at a higher level than the forwardbottom portion adjacent the step, said boat further comprising means foradmitting gas to the space below said rearward bottom portion.

According to the present invention, said step extends from saidlongitudinal vertical plane obliquely rearwardly towards the sides ofthe boat on each side of said vertical plane at least over part of therange between said plane and each side. Further, this step terminates ata distance from the side walls of the boat, the forward bottom portionthus merging, without astep being present, in the rearwardbottom portionat least at the extreme lateral parts of the rearward bottom portion.

In the following description the word air will be used for the cushionof gas introduced underneath the rearward portion of the bottom,although it will be understood that such gas may consist of a mixture ofpressurized air and exhaust gases, or other gases or gas mixtures.

With the arrangement of the bottom step as defined above, severalimprovements are obtained in comparison to known air cushion boats.

With a boat comprising a bottom step as defined above, certaindisadvantageous phenomena which have shown to be present with boatscomprising means for supplying.

air to the bottom thereof, are essentially eliminated, this being mainlydue to the fact that the supporting air cushion obtains a considerablesize as compared with the size 3,331,347 Patented July 18, 1967 of theboat bottom surface within the outer limits of the bottom surface incontact with the water during running, and this without air leakagewhich is necessarily present with partly airborne boats.

With a shape of the bottom step as mentioned above and the essentiallycontinuous merging of the forward portions of the bottom strakes withthe rearward ones adjacent the boat sides, the water seal along theedges of the air cushion underneath the rearward part of the boat bottomis greatly improved, such a seal being essential for the creation of alarge air cushion causing a favorable relation between boat speed anddriving force, the force necessary for creating the air cushion beintaken into account as well.

Furthermore, the shape of the step and the termination thereof adjacentor at a distance from the boat sides to letthe forward bottom portionlaterally merge into the aft portion of the bottom diminishes the risksof frictionincreasing water motion along and in contact with the bottomrearwardly of the step and wingwards.

Due to the small resistance caused by the boat hull in contact with thewater and the gas cushion, the resulting drag of the boat is extremelysmall. Further the friction resistance is very small due to the factthat the bottom skin portions which are in contact with the water duringrunning essentially constitute only .a minor sealing surface or evensealing line, the boat supporting forces being essentially created bythe air cushion pressure. Tests have evidenced, that a boat according tothe invention show the property, not usual for planing boats, ofobtainin g a very low total resistance force over a comparatively largerange of speed. Further, it has very good steering properties, the shapeof the step aiding in holding the supporting air cushion enclosedunderneath the bottom to an extent essentially reducing the totalresistance force.

Various features and advantages of the invention will be described indetail in connection with accompanying drawings, in which:

FIG. 1 is a longitudinal side view of a first embodiment of a boataccording to the invention;

FIG. 2 is a plan view of the boat shown in FIG. 1;

FIGS. 3ae are vertical cross sections in planes along lines IIIa, I111),I110, H112 and IIIe, respectively, of FIG. 2;

FIG. 4 illustrates, by way of an example, a shape of the step of theboat as viewed from aft towards stem, FIG. 4 illustrating the starboardpart of the boat bottom and side;

FIG. 5 is an inverted plan view of a further embodiment of a boataccording to the invention;

FIG. 6 is a section taken on line VI-VI of FIG. 5;

FIG. 7 is an inverted plan view of a further embodiment of a boatcomprising two steps;

FIGS. 8 and 9 schematically illustrate means for supplying air to thespace underneath the boat bottom rearward of the step;

FIG. 10 illustrates still another embodiment of a boat according to theinvention;

FIG. 11 is a side view of a boat comprising a plurality of steps;

FIG. 12 is an inverted plan view of the boat illustrated in FIG. 11;

FIG. 13 is a vertical section of the bottom skin of the boat illustratedin FIGS. 11 and 12 taken on line XIII XIII of FIG. 12;

FIG. 14 is a vertical section of the bottom surface taken on lineXIV-XIV of FIG. 12;

FIG. 15 is a vertical section of the bottom taken on line XV-XV of FIG.12;

XVI of FIG. 12;

FIG. 17 is a vertical cross sectional view of still anoth embodiment ofa boat;

F G. 18 is an inverted plan view of the boat illustrated in FIG. 17;

FIG. 19 is a cross sectional view of the boat illustrated in FIGS. 17and 18 taken on line XIX-XIX of FIG. 18; and

FIGS. 20 and 21 are cross sections through bars connecting portions ofsteps of the boat illustrated in FIGS. 17-19.

FIGS. 1 to 3 illustrate a first embodiment of a boat with a stepaccording to the invention. In FIGS. 1 to 3 there is shown a hull 1 ofthe boat having a bottom 2 rearwardly of the step, a bottom 3 forwardlyof the step, bilge lines 4 and a stern 5. The water level with the boatat rest is shown at 6-6. An air supply distribution duct 7 is fed froman air duct 8. A boat driving motor 9 drives a fan 10. Numeral 11represents side Walls of the hull and 12 designates the step between therearward portion 2 and the forward portion 3 of the bottom. A space 13is formed for an air cushion rearwardly of the step. Lines 1414represent the water level with the boat running at speed. 15 is thewetted range of the forward portion of the bottom during running, 15abeing the wetted portion of lateral parts of the rearward bottom portionconstituting lateral sealing surfaces or lines during running, 15b beingthe wetted aft bottom surface. Water is discharged during running oversmooth water along path 16 the bounds of which are shown by dash-dotlines 16a16a, during running over waves water is discharged along path17.

When at rest, the boat is displacing, the entire portion 2 of the boatbottom rearwardly of the step and major parts of the front portion 3 ofthe bottom, as well as portions of the side walls 11 above the bilges 4then being submerged as indicated by water level line 6-6 in FIG. 1.When the motor 9, and thus the fan as well, is started, air is suppliedthrough duct 8 to the air distribution duct 7, which extends along thestep 12 or a great part thereof. From the air distribution duct 7 theair enters the space 13 rearwardly of the step and underneath therearward bottom portion 2, said air constituting an air cushion withinthe space 13. Air supplied when the boat is at rest will then beexpelled along the boat sides. When the screw of the boat (notillustrated) is then coupled to the motor, the boat starts movingforward while air is supplied to the space 13. When the boat obtains itsfull speed or other high speed at which the boat is normally intended tobe used, the boat and in particular the rearward parts thereof willoccupy a higher position relative to the water level, as illustrated bywater level line 1414.

The fan 10 is so dimensioned, that, when the boat is running at speed,the fan delivers compressed air required for compensating theinavoidable leakage of air from the air cushion. The leakage of airarises for several obvious reasons, one object of the invention asmentioned above being to provide means to restrict such leakage andconsequently the energy consumed for generating the compressed air to anacceptable value, without jeopardizing other valuable characteristics ofthe boat as, for instance, stability and maneuverability on smooth wateras well as in rough sea.

One such cause of loss of air and one which is present also when theboat is moving over a smooth water surface, is that the air, even if thepressure of the air cushion is held very small, will be sucked outbackwardly by the water streaming towards the rear bottom portions undera very small angle of attack.

In the most common situation the water surface is, however, notcompletely smooth, which brings about an increase of air loss not onlyin a rearward and in a lateral direction, but incidentally in thedirection of movement of the boat as well.

When the water surface is smooth, the wetted surface is of the shapeillustrated at for the forward portion of 4 the bottom and at 15a and15b for the lateral and the rearmost parts, respectively, of therearward portion 2 of the bottom. The water discharge from the boat whenit moves on smooth water surface, is illustrated by path 16. When theforward portion of the bottom loses its contact with the water locally,a second type of water discharge will arise as well, this waterdischarge being schematically illustrated by path 17 in FIG. 2. Tests inpractice have shown that such discharge of water into the space of theair cushion is directed outwardly and upwardly, so as to strike thelateral parts of the rearward bottom portion 2 at a small angle. Withthe construction of the boat bottom as described, the resistance causedby such inward water discharge as illustrated by the path 17 is greatlyreduced.

FIG. 4 illustrates by way of example the shape of a step 12 as viewedfrom stern to stem, showing how the height of the step decreaseslaterally towards the bilge 4 to vanish entirely at or a short distancefrom the bilge. Experiments in practice have proven that, if H is thelargest step height within the center part of the bottom over about onethird of the boat breadth, the height of the step should preferablydecrease so as to obtain a value h=H 3 or less within about theoutermost /5 of the boat breadth. The angle B between the forward andrearward bottom portions adjacent the step should be less than 30 andpreferably less than 20.

Further improvements of the properties of a boat according to theinvention and in particular the properties of such a boat when running ahigh speed over a rough water surface will be evident from the followingdescription of further embodiments of a boat according to the invention.

FIGS. 5 and 6 illustrate an embodiment comprising a plurality of furthersteps 12a, 12b and 120 extending from a recess 34 in the bottom surfaceexending rearwardly of the front step 2 and connecting to a compressedair duct 37. The rearward part of the bottom comprises a center portion33 located at a higher level than the inner parts of lateral portions31, the raised center portion 33 causing a concentration of the air exitto the center portions of the stern and at a level to diminish thepossibility for the air to be sucked downwardly by the screw or screwswhen running in rough sea. The lateral portions 31 together constitute aV-shaped structure aiding in hydrodynamic stability of the boat.

FIG. 7 shows a boat comprising two steps, a step 35 of essentially thesame shape as the front step 12 being arranged rearwardly of the step12. The step 35 is arranged at such a level that normally, that is whenthe boat is moving over a smooth water surface, it does not contact thewater, but it aids in guiding water jets hitting the bottom skin betweenthe two steps to cause the water again to leave the skin and restore theair cushion. 16 and 17 represent the water discharge paths where theboat moves respectively over smooth and rough water.

FIG. 8 schematically illustrates the fan 10 for supplying air to thespace beneath the bottom rearward of the step and means to prevent waterfrom entering the fan under conditions for which the pressure underneaththe boat may exceed the pressure of the fan. For this purpose, theoutlet of the fan 10 connects to the air cushion space 13 by means of aduct 71 containing a non-return valve 72.

FIG. 9 schematically illustrates a duct system which utilizes theexhaust gases of the boat motor as a source of compressed gas. Theexhaust gas duct 73 connects to the space 13 via a non-return valve 72.A branch duct 74 of duct 73 between the exhaust gas manifold of themotor and non-return valve 72 connects to open air via a furthernon-return valve 75 to prevent creation of a vacuum sucking water intothe motor.

FIG. 10 illustrates an embodiment according to the invention comprisinga front step of conventional construction in the front portion 3 of thebottom. This step is arranged at a level such that when the boat ismoving at speed over calm water surface the step is raised over sealevel, while it improves the longitudinal stability when the boat ismoving over waves by the front bottom surface 81 occasionally contactingthe water, the step 80 aids in causing the water to hit the front bottomportion 3 adjacent the step 12 at an angle of attack essentiallycorresponding to the one prevailing when the boat is moving over calmwater. In this embodiment, the bilge line 4 has a point of inflection 82and is curved to correspond essentially to the water level downstream ofthe stem when the boat moves over calm water in the highest speed rangeto provide as far as possible an ideal sealing line or surface betweenboat bottom and water. Forward of the inflection point 82 the bilge lineis concave, viewed from above, and rearwardly of the point of inflectionit is convex, the rearmost porton of the rearward bottom portion 2ending in a V-shaped portion having a keel line 61 and the front part ofthe rearward bottom portion 2 having a section in lateral verticalplanes which is essentially convex upwardly.

Figs 11 and 12 illustrate a further development of a boat according tothe invention by which the properties of the boat when moving over arufiled sea is further greatly improved. In this embodiment a number offurther steps 112114 are arranged rearward of the step 12 and extendfrom the longitudinal vertical center plane obliquely forwardly towardsthe bilge line 4 to terminate at or before reaching the bilge line.Preferably, these steps 112-114 are curved so as to have a concave shapeas viewed from the stem of the boat. In tin's embodiment the air duct 8from fan 10 connects the air ducts 107 extending in the longitudinaldirection of the boat and having air outlet apertures 108 opening in theair cushion space adjacent and rearward of each step.

The steps 112-114 are arranged at such a level that, in principle, theyhave no effect or action when the boat is moving at high speed over acalm sea level. When the boat moves over a ruffied water surface bywhich water jets 17 of the type described above are dischargedrearwardly of the front step 12, said jets are taken care of by asuccessive concave step towards which the jets originally leaving thefront step 12 .are essentially perpendicular or at least constitute anangle not far from 90. Although steps of the kind described inconnection FIGS. 5-7 essentially improve the running characteristics ofthe boat on ruffled sea, a still more favorable result is obtained witha shape of the steps as illustrated in FIGS. 11 and 12.

As mentioned above FIGS. 13-15 illustrate sections taken on the linesXIII, XIV and XV, respectively, of FIG. 12. In FIG. 15, a is the angleof attack of a normally wetted part of the rearward bottom portion 2when the boat is running on calm water. The size of angle a should bebetween 3 and 12, and preferably between 6 and 9.

FIG. 16, which is a section on the curved line XVI of FIG. 12 along step113, illustrates the air channel 107 extending between an internalbottom plating 104 and the rearward bottom portion 2, which in FIG. 16is represented by step 113. FIG. 16 illustrates how the steps terminateat a point 139 located a distance from the bilge line 4, leaving a rimsurface 132 on the rearward bottom portion 2 constituting a continuousextension to the forward bottom portion 3 laterally of the front step12.

FIGS. 17-19 illustrate an embodiment essentially corresponding the oneillustrated in FIGS. 1116, in which,

however, a central air distribution channel 215 extends centrally of theboat. This channel 215 opens downwardly over its entire length andextends sufiiciently far in the forward and rearward direction, so thatair is admitted to all the spaces beneath the rearward bottom portion 2and between each two successive steps. As evident from the sectionillustrated in FIG. 19, this embodiment makes it possible to constructthe boat bottom in one continuous shell. The compressed air duct 8 opensinto the roof 216 of channel 215. The steps 211-214 which are concave asviewed from the stem, are located rearwardly of the convex step 12 andbridge over the channel 215, constituting thereat flat bars 218, thelower surfaces of which have an angle of attack making the bars suitableto act either as hydrofoils, as illustrated by a section of a bar shownin FIG. 20 or as a step, as illustrated by the bar section shown in FIG.21. In the latter case, the bar has a downstream end wall essentiallyperpendicular to the direction of motion of the boat.

What is claimed is:

1. A high speed boat comprising a boat hull having lateral bilge linesand including a bottom having a forward bottom portion and a rear bottomportion, said forward bottom portion terminating rearwardly in a stepseparatmg sa1d forward bottom portion from the rearward bottom portion,said rearward bottom portion having a foremost part which adjacent thestep is located on a higher level than the forward bottom portionadjacent the step, to thereby define a space below the rearward bottomportion, means for generating and admitting compressed gas to the spacebelow said rearward bottom portion, said step extending from the centerlongitudinal vertical plane of the boat obliquely rearwardly towards thebilge lines of the boat on either side of said vertical .plane at leastover the major part of the distance between said plane and each bilgeline to terminate laterally adjacent the bilge lmes so that the forwardbottom portion merges with the rearward portion at least at the extremelateral regions of the rearward bottom portion adjacent the bilge lines,said rearward bottom portion adjacent the stern on either side of saidvertical plane having surfaces which form angles with said plane lessthan at least one further step extending over part of the rearwardbottom portion rearwardly of the first said step between said forwardand rearward bottom portions, each further step extending obliquelyforwardly towards the bilge lines and terminating at or before reachingthe same.

2. A high speed boat as claimed in claim 1 comprising a central airdistribution channel in connection with said means for generatingcompressed gas, said channel extending centrally of the boat and beingopen downwardly toward the space below the rearward bottom portion, saidfurther step extending laterally across said channel in the form of abar having a lower face located at a level beneath the rearward bottomportion on either side of the channel.

References Cited UNITED STATES PATENTS 1,121,006 12/1914 Fauber114--66.5 2,450,665 10/ 1948 Jutte 114-665 2,555,307 6/1951 Alysworth114-66.5

FOREIGN PATENTS 418 1877' Great Britain. 1,243,460 9/1960 France.

MILTON BUCHLER, Primary Examiner. A. H. FARRELL, Examiner.

1. A HIGH SPEED BOAT COMPRISING A BOAT HULL HAVING LATERAL BILGE LINESAND INCLUDING A BOTTOM HAVING A FORWARD BOTTOM PORTION AND A REAR BOTTOMPORTION, SAID FORWARD BOTTOM PORTION TERMINATING REARWARDLY IN A STEPSEPARATING SAID FORWARD BOTTOM PORTION FROM THE REARWARD BOTTOM PORTION,SAID REARWARD BOTTOM PORTION HAVING A FOREMOST PART WHICH ADJACENT THESTEP IS LOCATED ON A HIGHER LEVEL THAN THE FORWARD BOTTOM PORTIONADJACENT THE STEP, TO THEREBY DEFINE A SPACE BELOW THE REARWARD BOTTOMPORTION, MEANS FOR GENERATING AND ADMITTING COMPRESSED GAS TO THE SPACEBELOW SAID REARWARD BOTTOM PORTION, SAID STEP EXTENDING FROM THE CENTERLONGITUDINAL VERTICAL PLANE OF THE BOTTOM OBLIQUELY REARWARDLY TOWARDSTHE BILGE LINES OF THE BOAT ON EITHER SIDE OF SAID VERTICAL PLANE ATLEAST OVER THE MAJOR PART OF THE DISTANCE BETWEEN SAID PLANE AND EACHBILGE LINE TO TERMINATE LATERALLY ADJACENT THE BILGE LINES SO THAT THEFORWARD BOTTOM PORTION MERGES WITH THE REARWARD PORTION AT LEAST AT THEEXTREME LATERAL REGIONS OF THE REARWARD BOTTOM PORTION ADJACENT THEBILGE LINES, SAID REARWARD BOTTOM PORTION ADJACENT THE STERN ON EITHERSIDE OF SAID VERTICAL PLANE HAVING SURFACES WHICH FORM ANGLES WITH SAIDPLANE LESS THAT 90*, AT LEAST ONE FURTHER STEP EXTENDING OVER PART OFTHE REARWARD BOTTOM PORTION REARWARDLY OF THE FIRST SAID STEP BETWEENSAID FORWARD AND REARWARD BOTTOM PORTIONS, EACH FURTHER STEP EXTENDINGOBLIQUELY FORWARDLY TOWARDS THE BILGE LINES AND TERMINATING AT OR BEFOREREACHING THE SAME.